Well, start with this:
https://www.cnn.com/2020/11/01/politics/mask-mandate-fact-ch...
https://www.cnn.com/2020/11/01/politics/mask-mandate-fact-ch...
> "I don't think that the statute can be read broadly enough to apply to all people merely moving on an interstate highway," Blackman said. "Once you go beyond people in federal facilities, you're really intruding on what the state's responsible for."
At best, they can cover Federal buildings with a policy. That is it.
Given that these roadways in question are interstate the federal government's power to regulate activity thereon is assumed as the power to regulate interstate commerce is one of the constitutionally enumerated powers of the federal government.